SB 


SOfl 


LIBRARY 


UNIVERSITY  OF  CALIFORNIA. 


RECEIVED    BY   EXCHANGE 


Class 


The 

Atomic  Weight 

of 

VANADIUM 


THESIS 


PRESENTED   TO    THE    FACULTY  OF  THE  GRADUATE  SCHOOL 

OF  THE  UNIVERSITY  OF  PENNSYLVANIA  IN  PARTIAL 

FULFILMENT  OF  THE  REQUIREMENTS  FOR  THE 

DEGREE  OF  DOCTOR  OF  PHILOSOPHY 


BY 

D.  J.  McADAM,  JR. 
WASHINGTON,  PA, 

1910 


PHILADELPHIA 
THE  JOHN  C.  WINSTON  CO 

IQIO 


The 

Atomic  Weight 

of 

VAN  ADI UM 


THESIS 

PRESENTED   TO    THE    FACULTY  OF  THE  GRADUATE  SCHOOL 

OF  THE  UNIVERSITY  OF  PENNSYLVANIA  IN  PARTIAL 

FULFILMENT  OF  THE  REQUIREMENTS  FOR  THE 

DEGREE  OF  DOCTOR  OF  PHILOSOPHY 


BY 

D.  J.  McADAM,  JR. 

WASHINGTON,  PA. 

1910 


PHILADELPHIA 

THE  JOHN  C.  WINSTON  CO. 
1910 


ACKNOWLEDGMENT. 

The  writer  wishes  to  express  his  thanks  to  Dr.  Edgar 
F.  Smith  for  his  kindness,  encouragement  and  valuable 
advice.  This  work  was  undertaken  at  Dr.  Smith's  sug- 
gestion and  carried  on  under  his  supervision. 

The  writer's  sincerest  thanks  are  also  due  to  Prof.  W. 
B.  Schober,  of  Lehigh  University,  for  the  use  of  the  labo- 
ratory and  of  valuable  apparatus  in  the  completion  of  this 
work,  also  to  Mr.  F.  B.  Kingsbury  and  Mr.  C.  A.  Pierle  for 
valuable  assistance. 


INTRODUCTORY. 

In  this  laboratory,  use  has  frequently  been  made  of  dry 
hydrochloric  acid  gas  in  making  various  separations,  and 
in  several  atomic  weight  determinations. 

Smith  and  Hibbs  (J.  Am.  Ch.  S.  16,  578;  Zeit.  Anorg. 
Ch.  7,  41)  found  that  vanadium  as  well  as  a  number  of 
other  substances  could  be  completely  volatilized  from  their 
alkali  salts  by  heating  in  a  current  of  dry  hydrochloric  acid 
gas.  It  therefore  seemed  probable  that  this  method  might 
be  used  in  determining  the  atomic  weight  of  vanadium. 

A  new  determination  of  the  atomic  weight  of  this  ele- 
ment would  be  particularly  desirable  since  the  result*  ob- 
tained by  previous  investigators  differ  widely. 

Historical. 

Berzelius,  in  1831  (Kongl.  Vet.  Acad,  Handl.  1-65; 
Ann.  Phys.  22,  1-67),  made  four  determinations  of 
the  atomic  weight  of  vanadium.  In  three  of  these,  he 
reduced  V2O5  to  V2O3  by  heating  in  a  stream  of  hydrogen ; 
in  the  fourth,  he  reoxidized  the  V2O3  to  V2O5.  As  the 
average  of  four  fairly  concordant  results  he  obtained  a 
value  which  corresponds  to  52.46,  referred  to  oxygen  as  16. 
As  Roscoe  pointed  out  later,  Berzelius'  material  undoubt- 
edly contained  phosphorus,  a  small  trace  of  which  inter- 
feres greatly  with  the  reduction  of  V2O5  to  V2O3.  The 
ammonium  molybdate  test  for  phosphoric  acid  was 
unknown  in  Berzelius'  time. 

Roscoe,  in  1867  (Phil.  Trans.  R.  S.  158,  1-27),  made 
four  determinations  by  the  method  of  Berzelius,  using 
material  carefully  purified  in  several  different  ways.  The 
average  of  the  four  results  was  51.371,  but  the  maximum 
and  minimum  differed  by  nearly  one-half  of  one  per  cent. 

3 


228324 


He  also  obtained  a  series  of  nine  values  by  determining 
the  amount  of  silver  required  to  precipitate  the  chlorine 
from  vanadium  oxychloride,  VOC13.  He  did  not  use  the 
proper  end  point  for  this  reaction,  but  the  final  results 
would  not  be  affected  very  much  by  this  error;  loss  of 
chlorine  on  the  treatment  of  the  VOC13  with  water  was 
probably  a  more  serious  source  of  error. 

In  still  another  series  of  eight  experiments,  Roscoe 
weighed  the  silver  chloride  obtained  from  a  known  weight 
of  vanadium  oxychloride.  He  does  not  mention  any  cor- 
rection for  the  solubility  of  the  silver  chloride  in  the  wash 
water.  If  this  was  neglected,  his  value  for  the  percentage 
of  the  chlorine  is  too  low,  and  consequently  his  value  for  the 
atomic  weight  is  too  high.  The  variation  in  the  percentage 
of  chlorine  in  these  seventeen  experiments  is  from  60.86 
to  61.55,  or  about  1.13  per  cent.  This,  of  course,  means  a 
variation  of  1.13  per  cent,  in  the  calculated  molecular 
weight  of  VOC13 ;  and,  since  the  atomic  weights  of  oxy- 
gen and  chlorine  are  assumed  to  be  known,  all  this  varia- 
tion would  apply  to  the  vanadium  alone,  and  would  amount 
to  about  3.4  times  1.13  or  3.84  per  cent.  For  example,  the 
maximum  calculated  value  for  the  atomic  weight  would  be 
52.39,  and  the  minimum,  50.44.  The  average  of  his  results 
by  both  methods  is  51.24. 

For  over  forty  years,  our  knowledge  of  the  atomic 
weight  of  this  element  rested  entirely  on  the  work  of  Ros- 
coe. Within  the  last  year,  however,  two  articles  on  the 
atomic  weight  of  vanadium  by  Wilhelm  Prandtl  and  Benno 
Bleyer  have  appeared.  (Zeit.  Anorg.  Chem.  65,  152  and 
67,  257.)  These  authors  have  used  the  same  methods  that 
were  used  by  Roscoe,  but  have  used  great  care  in  avoiding 
the  sources  of  error  in  the  work  of  the  earlier  author. 

The  vanadium  oxychloride  was  carefully  purified,  and 
kept  out  of  contact  with  air  until  it  had  been  weighed. 


Moreover,  on  treatment  of  the  oxychloride  with  water,  they 
reduced  the  vanadium  to  the  valence  of  four  by  means  of 
pure  zinc,  and  thus  avoided  loss  of  chlorine. 

In  order  to  make  allowance  for  the  solubility  of  silver 
chloride  in  water,  they  prepared  twelve  wash  waters  and 
used  them  in  regular  order.  These  were  prepared  by  wash- 
ing the  silver  chloride  precipitated  in  the  first  experiment 
in  each  series,  the  twelve  filtrates  being  preserved  in  the 
same  order  in  which  they  were  obtained. 

In  the  first  article  published  by  Prandtl  and  Bleyer 
are  given  the  results  of  two  series  of  experiments  by  this 
method.  In  series  i,  consisting  of  five  determinations  (the 
first  one  being,  of  course,  rejected),  the  average  percentage 
of  chlorine  obtained  from  the  oxychloride  was  61.3095  ± 
0.0158;  the  maximum  was  61.352  and  the  minimum  61.284, 
a  variation  of  o.n  per  cent.  This  variation  when  applied 
to  the  vanadium  content  would  be  multiplied  by  3.4,  making 
0.37  per  cent,  variation  in  the  calculated  values  for  the 
atomic  weight.  The  average  value  for  the  atomic  weight 
in  this  series  is  given  as  51.133  ±  0.013.  The  authors, 
however,  have  overlooked  the  fact  that  the  probable  error 
in  the  percentage  of  chlorine  must  be  multiplied  by  3.4  to 
give  the  probable  error  in  the  atomic  weight  of  vanadium. 
So  it  should  be  ±  0.044  instead  of  db  0.013. 

In  series  II,  consisting  of  six  determinations,  the  aver- 
age percentage  of  chlorine  was  61.3696  ±  0.0098,  the 
extremes  being  61.405  and  61.348,  a  variation  of  0.093  Per 
cent. ;  this  would  correspond  to  a  variation  of  0.316  per 
cent,  in  the  atomic  weight.  The  average  value  for  the 
atomic  weight  in  the  series  is  50.963,  and  the  probable 
error,  as  before,  should  be  multiplied  by  3.4,  giving  ±  0.027 
instead  of  0.008.  As  a  mean  of  the  two  series  they  get 
51.048  ±  o.oio,  but  it  should  be  ±  0.034. 

In  the  second  article,  by  the  same  authors,  they  have 
a  third  series  of  four  accepted  values  varying  from  61.301 


6 

to  61.333  for  percentage  of  chlorine.  As  an  average  for 
the  thirteen  accepted  values  in  the  three  series,  they  obtain 
51.061  for  the  atomic  weight. 

In  the  same  article,  these  authors  have  recorded  the 
results  of  four  determinations  by  the  method  of  Berzelius. 
In  this  series,  they  obtained  results  that  are  considerably 
higher,  giving  an  average  of  51.374  ±  0.033.  But  they 
found  that  the  V2O3  takes  up  oxygen  so  rapidly  that  the 
weight  of  the  compound  cannot  be  obtained  with  any  cer- 
tainty. It  is,  therefore,  probable  that  the  observed  weights 
of  V2O8  are  too  great,  and  consequently  the  calculated 
values  for  the  atomic  weight  of  vanadium  are  too  high. 

The  discrepancies  in  the  results  of  their  careful  inves- 
tigation have  thus  made  more  evident  the  need  for  a  rede- 
termination  of  the  atomic  weight  of  vanadium  by  a  new 
method. 

Method  and  Apparatus. 

The  salt  of  vanadium  used  in  these  experiments  was 
sodium  meta-vanadate  (NaVO8),  the  most  stable  of  the 
vanadates  of  sodium.  Some  attempts  were  made  to  use 
other  vanadates  of  sodium,  but  all  except  the  meta-vana- 
date were  found  to  be  unstable  or  indefinite. 

The  meta-vanadate  was  heated  in  hydrochloric  acid 
gas  in  order  to  drive  out  the  vanadium  and  leave  sodium 
chloride.  Suice  hydrochloric  acid  has  a  tendency  to  reduce 
vanadates,  it  seemed  probable  that  a  mixture  of  hydro- 
chloric acid  and  chlorine  would  drive  out  the  vanadium 
more  readily  than  the  hydrochloric  acid  alone.  Experi- 
ments proved  that  the  presence  of  a  small  proportion  of 
chlorine  had  a  good  effect. 

The  apparatus  was  constructed  entirely  of  glass,  with 
connections  of  ground  glass  or  sealed  by  sulphuric  acid. 
The  arrangement  of  the  gas  generators  and  drying  appara- 
tus is  shown  in  Fig.  I. 


In  the  vessel  A,  the  hydrochloric  acid  gas  is  generated 
by  allowing  concentrated  sulphuric  acid  to  drop  into  strong 
hydrochloric  acid  solution.  In  B,  the  chlorine  is  gener- 
ated by  allowing  hydrochloric  acid  to  drop  into  the  flask 
containing  pure  potassium  permanganate  moistened  with 
water.  C,  C,  are  drying  vessels  containing  sulphuric  acid. 


FIG.  i 

D,  D,  D  are  connectors  in  which  sulphuric  acid  is  placed 
so  as  to  make  the  connection  air  tight.  E  is  a  drying  tower 
containing  glass  beads  moistened  with  sulphuric  acid.  F,  F 
are  stop-cocks  so  arranged  that  the  gas  from  the  generators 
can  be  shut  off  and  a  current  of  pure  air  substituted. 

Several  modifications  were  made  in  the  apparatus  con- 
taining the  sodium  vanadate,  before  the  best  form  was 
obtained.  These  are  shown  in  Figs.  2  and  3. 


PREPARATION  OF  PURE  MATERIAL. 

Water. 

The  distilled  water  of  the  laboratory  was  redistilled 
once  from  alkaline  permanganate,  rejecting  the  first  fourth 
of  the  distillate.  It  was  then  redistilled  twice  more,  the  last 
time  with  a  block  tin  condenser;  in  some  of  the  later 
preparations  a  quartz  condenser  was  used.  The  water 
seal  invented  by  T.  W.  Richards  was  used  in  all  distillations. 
When  used  for  crystallizations,  the  water  was  either  allowed 
to  run  from  the  condenser  directly  into  a  platinum  dish, 
or  was  collected  in  a  quartz  flask. 

Sodium  Meta-Vanadate. 

The  chief  source  was  the  iron  vanadate  that  is  used  in 
the  preparation  of  ferro-vanadium.  It  contained  not  more 
than  a  trace  of  phosphorus  or  molybdenum. 

The  iron  vanadate  was  changed  to  sodium  vanadate 
by  boiling  with  caustic  soda  or  sodium  carbonate,  filtering 
off  the  ferric  hydroxide,  and  evaporating  the  filtrate  to 
crystallization.  It  was  purified  by  several  different  methods. 

Sample  A. 

A  mixture  of  vanadic  acid  and  acid  vanadates  of 
sodium  was  boiled  with  a  slight  excess  of  C.  P.  sodium 
carbonate.  It  was  then  recrystallized  five  times  in  glass 
from  ordinary  distilled  water,  and  twice  in  platinum  from 
twice  distilled  water.  The  crystallization  was  carried  on 
in  a  room  free  from  acid  fumes,  so  no  special  precautions 
were  taken  to  keep  the  material  out  of  contact  with  the 
air  of  the  room.  The  sample  was  dried  and  preserved  in 
porcelain  dishes  in  a  desiccator,  over  sulphuric  acid  that 
had  been  boiled  with  ammonium  sulphate. 


9 

Sample  B. 

Some  meta-vanadate  containing  phosphates  was 
recrystallized  a  few  times,  rejecting  the  first  crop  of  crys- 
tals each  time.  The  phosphate  was  thus  almost  completely 
removed.  The  partially  purified  meta-vanadate  was  now 
recrystallized  six  times  in  glass  and  once  in  platinum  from 
twice  distilled  water,  being  drained  by  suction  each  time. 

It  was  next  crystallized  six  times  more  in  platinum  by 
dissolving  in  hot  water,  cooling,  and  distilling  into  the  dish 
some  twice  distilled  alcohol.  The  substance  separated  out 
in  small  crystals  and  settled  rapidly,  leaving  a  large  volume 
of  liquid,  which  was  poured  off.  It  was  then  recrystallized 
twice  from  water  by  allowing  the  crystals  to  form  slowly 
without  stirring ;  for  each  crystallization  several  weeks  were 
required,  and  considerable  liquid  was  left,  which  was  poured 
off.  The  substance  was  dried  and  kept  for  about  two  years 
in  a  desiccator  over  caustic  soda. 

Sample  C. 

Some  sodium  vanadate,  which  had  been  crystallized 
several  times,  was  recrystallized  twice  more  in  porcelain, 
from  ordinary  distilled  water.  It  was  then  recrystallized 
in  platinum  three  times  from  ordinary  distilled  water  and 
three  times  from  thrice  distilled  water.  It  was  kept  in  a 
desiccator  over  caustic  soda  during  crystallization. 

Centrifugal  drainage  was  used  in  the  last  five  crys- 
tallizations. The  centrifugal  machine  had  an  arrangement 
by  which  the  material  could  be  placed  in  a  perforated  plati- 
num cone.  Not  enough  time  was  allowed  to  each  crystal- 
lization, consequently  the  crystals  formed  in  a  pasty  mass, 
which  did  not  drain  well.  This  error  was  avoided  in  later 
preparations. 

The  crystals  were  now  dissolved  in  hot  water  and 
allowed  to  stand  in  a  desiccator  over  caustic  soda ;  crystals 
formed  slowly  and  the  remaining  liquid  was  poured  off. 


10 


The  solution  was  yellow  at  first,  but  as  crystallization  pro- 
ceeded it  became  colorless. 

The  fused  material  was  quite  hygroscopic,  indicating 
that  it  still  contained  an  excess  of  alkali. 

Sample  D. 

The  mother  liquor  from  sample  C  was  put  in  a  desicca- 
tor over  caustic  soda  and  allowed  to  evaporate  to  dry- 
ness.  A  little  over  two  grams  were  obtained,  and  this  was 
used  later  as  a  test  of  the  neutrality  of  sample  C. 

It  showed  some  excess  of  alkali. 

Sample  E. 

Since  sample  C  still  contained  excess  of  alkali,  a  por- 
tion of  it  was  recrytallized  twice  more  with  centrifugal 
drainage,  and  was  washed  each  time  with  a  little  distilled 
water.  The  crystallization  was  allowed  to  take  place 
slowly,  so  that  the  substance  was  not  pasty  as  in  sample  C ; 
consequently  it  drained  readily,  giving  a  light  yellow  fil- 
trate. Contact  with  the  air  of  the  room  was  prevented  as 
much  as  possible  by  keeping  it  in  a  desiccator  over  caustic 
soda  during  crystallization. 

The  material  had  now  been  put  through  eleven  crys- 
tallizations altogether,  and  was  apparently  free  from  excess 
of  alkali. 

While  the  fused  material  of  sample  C  was  so  hygro- 
scopic that  it  could  hardly  be  weighed  to  o.oooi  gm.  the 
weight  of  sample  E  could  be  obtained  without  difficulty  to 
o.ooooi  gm. 

Sample  F. 

Crude  sodium  vanadate  was  acidified  with  sulphuric 
acid,  and  the  precipitated  vanadic  acid  washed  repeatedly 
with  distilled  water,  but  it  still  gave  a  test  for  sulphuric 
acid. 


II 


It  was  then  treated  with  a  large  quantity  of  water, 
and  reduced  to  vandyl  oxalate  by  heating  with  oxalic  acid. 
A  slight  excess  of  ammonium  oxalate  was  added  and  the 
double  ammonium  oxalate  crystallized  out  on  evaporation 
and  cooling.  After  three  crystallizations,  with  drainage  by 
suction,  no  trace  of  sulphate  could  be  detected,  and  the 
material  was  probably  free  from  phosphoric  and  molybdic 
acids. 

By  addition  of  excess  of  ammonia,  a  brown  precipi- 
tate of  ammonium  vanadate  was  obtained  which  was  fil- 
tered and  washed  several  times.  It  was  then  heated  to  get 
rid  of  ammonia,  and  fused  with  sodium  carbonate.  Since 
the  water  solution  was  still  greenish,  the  oxidation  was  com- 
pleted by  addition  of  a  little  sodium  peroxide.  The  analy- 
ses of  the  sodium  carbonate  and  sodium  peroxide,  accord- 
ing to  J.  T.  Baker,  showed  the  following : 

Na2COs  Na.0, 

Fe    0.0005%  Fe    0.003  % 

A12O«  0.0002%  A12O« o.ooi  % 

CaO    0.008  %  Cl  .' . .  0.007  % 

SiO2   o.ooi  %  SO»   o.ooi  % 

Cl  0.085  %  Na2O3    83.1      % 

SOs o.ooi  %  COa  0.32    % 

H,O  0.95    % 

The  sodium  vanadate  was  now  crystallized  eight  times 
in  porcelain  and  three  times  in  platinum,  from  ordinary  dis- 
tilled water,  suction  being  used  after  each  crystallization. 
It  was  now  practically  neutral  to  phenol-phthalein. 

It  was  next  crystallized  four  times  more  from  thrice 
distilled  water,  each  time  with  centrifugal  drainage  and 
washing.  The  last  three  times  the  water  came  in  contact 
with  nothing  but  quartz  and  platinum.  Special  precautions 
were  taken  to  avoid  contact  with  carbon  dioxide  of  the  air 
during  the  last  few  crystallizations. 


12 


The  effect  of  carbon  dioxide  of  the  air  could  be  only 
slight,  but  experiments  showed  that  it  affects  the  equi- 
librium to  a  certain  extent.  The  gas  prepared  by  the  action 
of  dilute  sulphuric  acid  on  sodium  bicarbonate,  washed  in  a 
sodium  bicarbonate  solution,  was  passed  through  a  vessel 
containing  glass  beads  moistened  with  water,  and  introduced 
into  a  nearly  colorless  solution  of  meta-vanadate,  which  it 
soon  turned  to  a  deep  orange  red.  The  equation  might  be 
represented  as  follows: 


4NaVO3  +  H2O  +  2CO2  =  Na2V4Ou  +  2NaHCO,. 

On  boiling  this  orange  colored  solution,  or  putting  it 
in  a  desiccator  over  caustic  soda,  the  reverse  reaction  takes 
place,  CO2  is  given  off  and  the  solution  becomes  colorless. 
If  the  meta-vanadate  contains  excess  of  alkali  or  sodium 
carbonate,  only  a  faint  yellow  color  appears  on  passing  in 
CO2,  since  the  increased  mass  of  bicarbonate  favors  the 
reverse  reaction. 

Meta-vanadate  solutions  are  usually  colorless  when  hot, 
and  yellow  when  cold,  but  an  experiment  tried  on  some  of 
the  pure  material  seems  to  indicate  that  the  yellow  color  is 
due  to  traces  of  acid  vanadate  caused  by  CO2  of  the  air. 
A  solution  of  the  meta-vanadate,  which  was  light  yellow 
in  color,  was  heated  to  boiling  in  a  glass  flask.  On  cooling 
in  contact  with  air,  a  yellow  color  appeared  ;  but,  if  the  flask 
was  stoppered  while  the  liquid  was  boiling,  no  color 
appeared  on  cooling. 

These  experiments  prove  that  CO2  of  the  air  can  have 
no  effect  on  the  solutions  when  they  are  hot;  therefore,  its 
effect  would  be  negligible  in  preparing  sodium  meta-vana- 
date, if  the  material  is  kept  in  a  desiccator  over  caustic 
soda. 

The  substance  which  had  thus  been  put  through  fif- 
teen crystallizations  was  cream  colored.  It  was  neutral  in 


13 

hot  or  cold  solution  to  methyl  orange,  litimus  or  phenol- 
phthalein.  The  fused  substance  was  colorless  and  trans- 
parent. 

Samples  G,  H  and  I  have  not  been  finished,  but  are  to 
be  used  in  later  work. 

Sample  G. 

Iron  vanadate  was  boiled  with  caustic  soda,  filtered 
and  acidified  with  sulphuric  acid.  The  preciptated  vanadic 
acid  was  washed  twice  with  water  and  then  heated  with 
sulphuric  and  oxalic  acids ;  by  this  process  the  vanadium 
was  reduced  from  the  valence  five  to  the  valence  four,  and 
with  the  sulphuric  acid  formed  vanadyl  sulphate,  V2O4  3SO3. 
On  evaporation,  small  blue  deliquescent  crystals  were 
formed,  which  were  filtered  from  the  syrupy  liquid  with 
suction.  It  was  crytallized  five  times  in  this  way. 

After  the  thi'rd  crystallization,  it  was  tested  for  phos- 
phoric acid  by  adding  ammonium  molybdate  and  nitric  acid, 
dissolving  the  reddish  brown  precipitate  in  ammonia  and 
adding  magnesia  mixture,  and  alternating  with  ammonium 
molybdate  and  magnesia  mixture  until  a  yellow  precipitate 
of  phospho-molybdate  was  obtained.  The  amount  was 
quite  small,  and  a  comparison  test  showed  it  to  be  less  than 
o.i  per  cent. 

After  the  fifth  crystallization  of  the  vanadyl  sulphate, 
it  was  dissolved  in  a  large  quantity  of  distilled  water,  and 
an  excess  of  sodium  carbonate  of  especial  purity,  accord- 
ing to  J.  T.  Baker,  was  added.  The  brownish  precipitate 
was  washed  fourteen  times  with  water  (in  which  its  solu- 
bility is  considerable),  but  it  still  showed  traces  of  sul- 
phates. 

In  order  to  convert  it  into  sodium  vanadate,  it  was  now 
treated  with  sodium  peroxide  having  the  following  anaysis, 
according  to  J.  T.  Baker : 

Fe.. 0.005%     A12O3.  .0.001%     Cl.. 0.002%     SO3.  .none, 
insoluble  matter trace,  phosphates  ^ none. 


14 

To  combine  with  the  excess  of  alkali,  CO2  was  passed 
into  the  liquid.  The  CO2  was  generated  by  action  of  sul- 
phuric acid  on  C.  P.  sodium  bicarbonate,  and  was  washed 
by  passing  through  three  bottles  of  distilled  water.  The 
solution  was  now  evaporated  to  crystallization  and  it  was 
necessary  to  leave  it  at  this  point. 

Sample  H. 

The  preparation  of  this  sample  was  begun  before  any 
of  the  others;  but,  since  it  was  not  possible  to  work  at  it 
continuously,  the  process  has  extended  over  several  years. 

Some  C.  P.  ammonium  vanadate  from  Kahlbaum  was 
treated  with  ammonium  sulpho-cyanide  acidified  with  hydro- 
chloric acid  and  shaken  with  ether.  A  slight  pink  color 
appeared  in  the  ether,  and  became  deeper  when  the  solution 
was  reduced  by  zinc,  thus  indicating  traces  of  iron  and 
molybdenum. 

In  order  to  remove  molybdenum,  the  ammonium  vana- 
date was  ignited  to  drive  off  ammonia  and  ammonium 
chloride,  and  was  dissolved  in  strong  HC1;  the  excess  of 
the  latter  was  removed  by  evaporation  and  the  residue  dis- 
solved in  water  and  filtered.  The  liquid  was  now  saturated 
with  H2S  and  heated  in  a  2^2  liter  pressure  flask  at  85°C. 
for  several  hours.  A  brown  precipitate  appeared,  which 
was  principally  V2S,,  and  should  contain  all  the  molyb- 
denum. 

The  next  process  was  to  remove  traces  of  arsenic.  The 
blue  filtrate  from  the  molybdenum  sulphide  was  evaporated 
and  oxidized  with  nitric  acid.  It  was  then  saturated  with 
ammonia,  diluted  to  four  or  five  liters,  and  saturated  with 
H2S ;  then,  from  the  ammonium  sulpho-vanadate  thus 
formed,  the  vanadium  sulphide  was  precipitated  by  HC1. 
The  sulphide  was  washed  several  times  by  decantation, 
dried,  and  gently  heated  in  a  hard  glass  tube  in  a  current 
of  dry  HC1  gas.  This  should  remove  the  arsenic,  according 
to  Smith  and  Hibbs. 


15 

The  remaining  V2S5  now  gave  no  test  for  molybdenum 
in  several  grams  of  material,  although  the  test  was  deli- 
cate enough  to  show  a  color  with  less  than  o.oooi  gm.  of 
MoO8. 

The  vanadium  sulphide  was  next  oxidized  with  redis- 
tilled nitric  acid  and  heated  to  form  V2O5.  In  order  to  vola- 
tilize the  vanadium  and  leave  behind  various  impurities, 
the  V2O5  was  then  heated  in  a  hard  glass  tube  in  dry  HC1 
gas.  (Smith  and  Hibbs,  Jr.  Am.  Ch.  S.  17,  682-686.) 
The  volatile  portion  was  collected  in  distilled  water,  evapo- 
rated, oxidized  with  redistilled  nitric  acid,  and  heated  to 
form  V2O5. 

The  purified  substance  was  now  dissolved  in  redis- 
tilled ammonia  in,  platinum  vessels  and  thle  excess  /of 
ammonia  boiled  off.  Acetic  acid  (which  gave  no  precipi- 
tate with  H2S,  NH4OH,  (NH4)2  C2O4  or  (NH4)2S)  was 
added  to  form  the  tetra-vanadate,  which  was  precipitated 
by  redistilled  alcohol,  and  the  supernatant  liquid  poured  off. 

After  standing  in  this  way  for  about  two  years,  it  was 
recrystallized  from  redistilled  water  and  the  liquid  removed 
by  centrifugal  drainage.  It  was  then  boiled  with  a  slight, 
excess  of  especially  pure  sodium  carbonate  until  no  more 
ammonia  fumes  were  given  off,  and  evaporated  to  crystalli- 
zation. 

Sample  I. 

An  acid  vanadate  of  magnesium  was  prepared  by  boil- 
ing vanadic  acid  with  excess  of  magnesia,  filtering,  con- 
centrating the  filtrate  and  adding  acetic  acid.  An  orange 
colored  crystalline  precipitate  was  formed,  which  could  be 
recrystallized  by  using  a  very  large  quantity  of  water ;  only 
a  few  grams  would  be  obtained  from  several  liters  of  water. 
With  each  crystallization,  some  of  the  salt  was  decomposed 
into  an  insoluble  acid  vanadate,  nevertheless,  about  eighty 
grams  passed  through  the  sixth  crystallization. 


i6 

Owing  to  the  large  amount  of  water  used,  this  ought 
to  be  free  from  impurities.  Even  after  the  third  crystalli- 
zation, it  gave  no  test  for  molybdenum  or  phosphoric  acid, 
although  the  original  material  contained  traces.  It  is 
intended  to  convert  this  magnesium  salt  into  sodium  vana- 
date  and  use  it  later. 

Hydrochloric  and  Sulphuric  Acids. 

For  all  but  the  last  two  experiments,  ordinary  C.  P. 
acids  were  used.  Since  the  method  of  generating  the  hydro- 
chloric acid  gas  was  a  purification  in  itself,  it  was  thought 
that  the  ordinary  acids  would  be  sufficiently  pure. 

If  the  hydrochloric  acid  contained  any  hydrobromic 
acid,  the  bromine  would  be  set  free  and  driven  out  by  the 
action  of  the  chlorine.  No  arsenic  would  remain  with  the 
sodium  chloride  in  the  final  weighing,  since  it  is  easily 
volatilized  by  heating  in  contact  with  hydrochloric  acid  gas. 
Any  sulphur  dioxide  in  the  sulphuric  acid  would  be  oxi- 
dized by  chlorine,  and  remain  in  the  drying  vessels. 

Nevertheless,  in  the  last  two  experiments,  special 
hydrochloric  and  sulphuric  acids  were  used,  containing  no 
arsenic,  nitric  acid,  or  sulphurous  acid,  and  only  a  trace 
of  iron,  according  to  the  analysis  of  J.  T.  Baker. 

Balance  and  Weights. 

A  Staudinger  balance  sensitive  to  o.ooooi  gm.,  was 
used  in  these  experiments.  It  was  kept  in  the  basement,  in  a 
room  that  was  used  for  no  other  work.  The  balance  rested 
on  a  brick  and  stone  support  that  was  sunk  directly  into 
the  ground. 

The  weights  were  kindly  loaned  by  Professor  Frank- 
lin, of  the  Physics  Department  of  Lehigh  University.  The 
larger  weights  were  of  brass,  gold  plated,  and  the  smaller 
weights  were  of  platinum.  They  were  carefully  standard- 
ized and  allowance  was  made  for  the  buoyancy  of  the  air; 


17 

the  standardization  was  repeated  several  times  in  the  course 
of  the  experiments. 

All  weighings  were  by  substitution,  and  were  cor- 
rected for  the  buoyancy  of  the  air.  A  counterpoise  was 
always  used,  of  the  same  size  and  material  as  the  vessel  to 
be  weighed,  and  the  vessel  was  always  left  near  the  bal- 
ance for  several  hours  before  weighing. 

Dehydration  of  the  Sodium  Meta-Vanadate. 

A  portion  was  heated  for  several  hours  at  385  °C.  in  a 
Caries  furnace  in  a  current  of  dry  air,  and  weighed.  After 
being  fused  and  again  weighed,  a  further  loss  of  0.05  per 
cent  was  observed. 

The  substance  melts  at  a  dull  red  heat  and  on  cooling 
forms  white  radiating  crystals,  slightly  hygroscopic.  If 
heated  for  a  time  at  bright  redness,  it  appears  to  lose  weight 
continuously,  although  very  slowly.  By  fusion  at  dull  red- 
ness, however,  it  is  easy  to  get  a  constant  weight. 

Specific  Gravity  of  Anyhydrous  Sodium  Vanadate. 

The  specific  gravity  of  the  fused  salt  was  determined 
by  putting  a  known  weight  of  the  substance  into  a  pyknom- 
eter,  filling  the  latter  with  alcohol,  and  weighing  it. 

The  weight  of  alcohol  required  to  fill  the  pyknometer 
was  14.593,  the  weight  of  sodium  vanadate  used  was  5-4375, 
the  weight  of  the  sodium  vanadate  and  alcohol  required  to 
fill  the  vessel  was  18.4335.  Therefore  the  weight  of  alcohol 
displaced  by  the  vanadate  was  14.593— (18.4335— 5.4375)  = 
i. 600.  Since  the  specific  gravity  of  the  alcohol  was  0.82, 
the  specific  gravity  of  the  sodium  vanadate  is 

5^37x0.82  =  2.79. 
i.  600 

Corrections  for  Buoyancy  of  the  Air. 
The  correction  for  the  weight  of  one  gram  of  sodium 
vanadate  is  equal  to  the  weight  of  i  c.  c.  of  air  multiplied 


i8 


by  the  difference  between  the  volume  of  one  gram  of  vana- 
date  and  I  gram  of  weights. 

The  temperature  varied  from  20°  C.  to  30°  C.  in  the 
progress  of  the  experiments,  but  the  pressure  did  not  vary 
much  from  750  mm. ;  the  average  correction  was,  therefore, 
calculated  for  25°  C.  and  750  mm.  The  weight  of  i  c.  c. 
of  air  under  those  conditions  is  0.00117,  the  volume  of  I 
gram  of  vanadate  is  0.358,  and  of  I  gram  of  brass,  0.119; 
therefore  the  correction  for  I  gram  of  vanadate  is  0.00117 
X  (o-358 — 0.119)  =  +  0.00028.  For  i  gram  of  sodium 
chloride,  using  the  accepted  value  2.14  for  the  specific 
gravity,  the  correction  is  0.00117  (0.468  — '0.119)  = 
+0.00041. 


Preliminary  Experiments  on  the  Action  of  Hydrochloric 
Acid  Gas  on  Sodium  Vanadate 

Some  sodium  vanadate  of  sample  A  was  placed  in  a 
porcelain  boat,  in  a  glass  tube,  through  which  a  mixture  of 
hydrochloric  acid  gas  and  chlorine  was  passed.  The  tube 
was  heated  to  385°  C.  in  a  Caries  furnace,  but  after  sev- 
eral hours  the  material  still  showed  by  its  color  the  pres- 
ence of  vanadium.  It  was  then  heated  in  a  combustion 
furnace  for  an  hour  and  a  half,  but  still  showed  a  yellow 
tinge.  Nevertheless,  it  was  weighed  and  the  amount  of 
vanadium  estimated  by  the  aniline  test  described  later.  It 
was  found  by  this  test  that  0.0013  gm.  of  V2O6  remained. 
The  corrected  weights  were: 

Wt.  of  Na  V  O, 0.8843 

"     "  Na  Cl 0.4241 

Assuming  the  atomic  weights  of  sodium  and  chlorine 
to  be  23.00  and  35.46,  respectively,  this  would  give  50.90 
for  the  atomic  weight  of  vanadium. 


19 

To  see  if  it  would  be  possible  to  remove  all  the  van- 
adium by  means  of  HC1  gas  and  chlorine,  a  still  smaller 
weight  of  sodium  vanadate  was  used;  yet  after  several 
hours'  heating,  the  residue  still  showed  a  yellow  color  and 
the  aniline  test  showed  0.003  gm.  V2O5.  The  corrected 
weights  were: 

Na  VOs 0.4538 

Na  Cl 0.2175 

This  would  give  50.97  for  the  atomic  weight. 

No  importance  is  attached  to  these  values,  for  the 
quantities  used  were  too  small. 

The  aniline  test  was  worked  out  by  Witz  and  Osmond 
(Bull.  Soc.  Chim.  (2)  45,309),  and  is  of  value  in  estimating 
very  small  quantities  of  vanadium.  It  depends  on  the  fact 
that  vanadium  salts  are  easily  oxidized  and  reduced,  and 
therefore  can  act  as  oxygen  carriers. 

If  a  solution  of  potassium  chlorate  is  added  to  a  solu- 
tion of  aniline  hydro-chloride,  heated  to  boiling  and  allowed 
to  stand  at  room  temperature,  no  coloration  appears.  If, 
however,  a  trace  of  vanadium  is  present,  a  color  appears, 
varying  from  light  yellow  to  black,  according  to  the  amount 
of  vanadium  present;  more  than  a  trace  of  vanadium  will 
cause  a  precipitate  of  aniline  black.  The  sensitiveness  is 
increased  by  the  presence  of  a  small  quantity  of  dilute  HC1, 
but  a  larger  quantity  will  cause  a  precipitation  of  aniline 
black,  even  when  no  vanadium  is  present 

In  making  this  test,  a  standard  vanadium  solution  was 
used,  containing  about  o.oooi  gm.  V2O5  to  I  c.  c. ;  this 
was  used  for  color  comparison,  as  in  the  Nessler  test  for 
ammonia,  and  in  neutral  solution  was  about  as  delicate. 

Since  the  vanadium  could  not  all  be  removed  by  treat- 
ment in  a  porcelain  boat,  some  trials  were  made  with  a  Jena 
glass  bulb  of  the  form  shown  in  Fig.  2,  a  form  used  by  T. 
W.  Richards  in  some  of  his  work. 


20 


G  is  the  bulb  containing  the  vanadium.  H,  H  are 
extra  bulbs  to  catch  any  material  that  may  spatter  out  of  G. 
I,  I  are  flasks  containing  water,  through  which  the  acid 
fumes  and  volatile  vanadium  compounds  are  drawn  by 
suction.  At  J  the  apparatus  is  connected  to  the  generator 
at  the  point  marked  J  in  Fig  I.  A  counterpoise  of  the  same 
size  and  shape  as  the  bulb  G  was  used,  and  the  difference 
in  weight  was  determined  by  substitution. 

The  sodium  vanadate  was  fused  in  a  platinum  capsule, 
then  powdered  and  transferred  to  the  bulb,  which  was  held 


FIG.  2 

slightly  inclined.  After  weighing  the  bulb  and  vanadate, 
it  was  heated  in  a  current  of  hydrochloric  acid  gas  and 
chlorine.  The  heat  was  furnished  by  Bunsen  burners  placed 
the  proper  distance  above  and  below  the  bulb ;  a  small  flame 
was  also  placed  under  the  exit  tube  and  thus  any  crawling 
of  material  prevented. 

When  as  much  as  possible  of  the  vanadium  had  been 
removed,  a  little  water  was  added  to  the  substance  in  the 
bulb  and  it  was  again  dried  in  the  stream  of  gas,  being 
rotated  at  the  last,  so  as  to  spread  the  material  over  the 
inner  surface  of  the  vessel.  In  this  process  the  sodium 
chloride  first  dissolved  in  the  water,  leaving  the  vanadium ; 


21 

then,  as  the  HC1  was  passed  in,  the  vanadium  dissolved 
and  the  sodium  chloride  crystallized  out.  As  the  liquid 
evaporated  the  vanadium  compound  was  left  at  the  surface, 
where  it  could  be  attacked  by  the  gases.  The  process  was 
thus  a  combination  of  crystallization  and  distillation. 

After  three  or  four  of  these  treatments,  the  vanadium 
could  all  be  driven  out  of  more  than  five  grams  of  vanadate, 
leaving  a  perfectly  white  residue,  which  gave  no  indication 
of  vanadium  by  the  aniline  test. 

After  displacing  the  hydrochloric  acid  gas  by  air,  the 
sodium  chloride  was  heated  nearly  to  fusion,  and  this 'was 
repeated  until  the  weight  was  constant. 

It  was  found,  however,  that  there  are  two  disadvan- 
tages to  this  form  of  apparatus.  The  fused  sodium  vana- 
date, which  is  slightly  hygroscopic,  takes  up  a  little  mois- 
ture while  it  is  being  pulverized  and  transferred  to  the  bulb. 
It  does  not  give  up  all  of  this  moisture  even  after  standing 
over  night  in  a  desiccator;  experiment  showed  that  seven 
grams  of  vanadate  retained  0.0025  gram  of  moisture  or 
0.035  per  cent.  But  the  most  serious  disadvantage  was 
that  the  sodium  chloride  decrepitated,  when  heated,  and  a 
small  quantity  was  thrown  out  of  the  vessel  into  the  extra 
bulbs  H. 

Nevertheless,  three  experiments  were  made  with  this 
form  of  apparatus,  using  material  of  sample  A.  In  each 
case  0.035  Per  cent-  was  subtracted  from  the  observed 
weight  of  sodium  vanadate  to  make  allowance  for  moisture, 
and  any  sodium  chloride  thrown  out  by  decrepitation  was 
weighed  and  its  weight  added  to  that  of  the  main  quantity. 
The  results  are  given  in  the  following  table: 


Weight, 
NaV03. 

Weight, 
NaCl. 

Molec.  Wt. 
NaVO3. 

Atomic  Wt., 
Vanadium. 

(I)      4-8850 
(2)      5-5793 
(3)     5.6975 

2-3393 
2.6691 
2.7244 

I22.O8 
I22.2O 
122.23 

51.08 
51.20 
51.23 

Average 51.17 


22 


Not  much  importance,  however,  is  attached  to  this 
value  on  account  of  the  uncertainty  of  the  corrections.  So, 
in  order  to  avoid  these  sources  of  error,  an  apparatus  of  the 
form  shown  in  Fig.  3  was  devised,  and  it  finally  proved  sat- 
isfactory. 

K  is  the  flask  containing  the  sodium  vanadate.  The 
small  bulbs  on  the  inner  and  outer  vessels  prevent  loss  by 
decrepitation;  and,  by  means  of  a  platinum  wire  fastened 
around  it  at  L,  the  flask  may  be  suspended  vertically  for 


FIG.  3. 


weighing.     M  is  a  quartz  dish  to  support  the  flask  while 
being  heated.    N  is  a  hard  glass  tube  used  as  a  connector. 

In  order  to  get  the  weight  of  the  sodium  vanadate,  it 
was  fused  in  a  platinum  capsule  and  rotated  just  before 
solidifying,  so  as  to  spread  the  substance  in  a  thin  layer. 
The  total  weight  of  capsule,  vanadate  and  a  platinum  rod 
was  then  taken.  By  means  of  the  platinum  rod,  the  vana- 
date was  then  broken  up  and  as  much  as  possible  trans- 
ferred to  the  flask,  which  was  held  vertically.  After  again 
heating  the  capsule  and  rod,  the  loss  of  weight  was  obtained, 


23 

which  was  the  weight  of  the  sodium  vanadate  transferred 
to  the  flask. 

The  heating  with  hydrochloric  acid  gas  and  chlorine 
was  the  same  as  in  the  experiments  with  the  glass  bulb. 
The  quartz  dish;  M,  was  heated  gently  by  a  Bunsen  burner, 
and  two  other  burners  were  arranged  above  the  vessel,  so 
as  to  radiate  sufficient  heat  downward.  After  about  four 
treatments  with  the  gas,  followed  each  time  by  adding  a 
little  water  and  again  drying  in  the  gas,  pure  sodium 
chloride  was  left.  The  white  color  of  this  substance  proved 
to  be  a  very  good  indication  of  its  freedom  from  vanadium. 
The  time  required  to  get  all  the  vanadium  out  was  about 
thirty  hours  of  actual  heating,  and  seemed  to  be  inde- 
pendent of  the  quantity  of  vanadate  used. 

An  attempt  was  made  to  use  a  Jena  glass  flask,  but  it 
cracked  at  a  critical  moment,  so  a  quartz  flask  with  straight 
neck  and  Jena  gjlass  inner  tube  was  next  tried.  Only  one 
experiment  was  completed,  because  the  inner  tube  fused 
in  contact  with  the  quartz,  when  the  sodium  chloride  was 
finally  heated  to  fusion.  The  results  of  this  experiment  are 
recorded  under  (i)  in  the  Table  on  page  (26).  The 
material  used  was  sample  A. 

It  was  necessary  to  send  to  Germany  and  have  two 
quartz  flasks  made  of  the  form  shown  in  Fig.  3,  with  both 
inner  and  outer  tubes  of  quartz.  For  this  reason  the  work 
had  to  be  left  for  a  year. 

An  advantage  of  the  use  of  the  quartz  apparatus  is 
that  the  sodium  chloride  could  be  heated  to  complete  fusion 
in  the  vessel  and  all  moisture  thus  removed.  It  was  found 
that  the  fusion  caused  practically  no  loss  by  volatilization, 
and  a  quite  definite  weight  for  the  salt  could  be  obtained. 
The  losses  on  heating  were  about  as  follows :  The  flask  and 
salt  were  weighed  after  fusion  of  the  salt  on  the  edges,  then 
after  complete  fusion,  there  would  be  a  loss  of  0.0012  gm. 


24 

After  again  fusing  it  for  several  minutes  to  the  highest 
temperature  of  the  blast  lamp,  there  would  be  a  further 
loss  of  o.oooi,  or  sometimes  0.0002  gm.  The  last  weight 
was  taken  as  correct.  The  bulb  on  the  inner  tube  nearly 
closes  the  outlet  to  the  flask,  when  it  is  held  vertically,  and 
this  evidently  prevents  loss  by  volatilization. 

Another  quartz  apparatus  of  the  same  size  and  shape 
was  used  as  a  counterpoise,  the  difference  in  weight  by  sub- 
stitution of  the  flask  and  counterpoise  being  taken.  On  the 
opposite  pan  of  the  balance  a  quartz  dish  of  the  same  weight 
was  used  as  a  tare.  It  was  necessary  to  leave  the  apparatus 
in  the  balance  case  for  several  hours  before  the  final  weigh- 
ing was  taken.  On  being  transferred  from  desiccator  to 
balance  case,  the  flask  seemed  to  lose  about  aooi  gm.  in 
weight  in  about  an  hour;  after  that  the  weight  would  be 
practically  constant.  The  loss  was  undoubtedly  due  to  the 
fact  that  the  flasks  were  filled  first  with  the  dry  air  of  the 
desiccator  and  then  with  the  moister  air  of  the  balance  case. 

After  getting  the  final  weight  of  the  flask  and  fused 
sodium  chloride,  the  flask  was  rinsed  out  with  distilled 
water,  heated  with  a  blast  lamp  and  again  weighed.  The 
difference  in  weight  is  recorded  in  the  Table  as  "loss  on 
rinsing/' 

In  experiment  II,  there  was  a  slight  increase  in  weight 
of  the  flask,  and  at  the  same  time  a  slight  greenish  yellow 
coloration  appeared  in  the  neck  of  the  flask.  The  yellow 
color  then  remained  through  all  the  experiments,  and  the 
weight  of  the  flask  was  practically  constant,  except  in 
experiment  IV,  where  there  was  a  considerable  gain  in 
weight  of  the  flask,  and  an  increase  in  the  yellowish  color 
on  the  neck.  The  deeper  color  persisted  until  the  inner  sur- 
face had  been  rubbed  with  a  cloth  moistened  with  various 
reagents,  such  as  acids,  ammonia  and  caustic  potash ;  this 
treatment  caused  the  color  to  become  lighter  and  brought 


25 

the  weight  back  to  normal.  On  heating  the  neck  of  the 
flask  with  the  blast  lamp,  the  yellow  color  would  travel 
around  to  the  opposite  side  from  the  flame,  but  could  not 
be  driven  away.  Our  explanation  is  that  some  vanadium 
vapors  were  taken  up  by  the  quartz  in  the  neck  of  the  appa- 
ratus, where  the  heat  was  much  less  than  in  the  body  of  the 
flask.  By  taking  the  loss  in  weight  on  rinsing,  this  would 
not  cause  any  error  in  the  results. 

The  solution  obtained  by  rinsing  out  the  vessel  showed 
a  very  slight  turbidity  which  looked  like  silica.  In  one 
case,  a  few  shining  scales  could  be  noticed,  which  evidently 
came  from  the  quartz  flask.  This  was  undoubtedly  due  to 
the  contraction  of  the  fused  sodium  chloride  on  cooling; 
although  it  was  spread  as  thin  as  possible,  it  always  broke 
apart  with  considerable  crackling.  The  solutions  obtained 
in  the  last  four  experiments  were  filtered  through  a  small 
filter  whose  ash  weighed  0.00003  gm.  After  ignition  in  a 
platinum  crucible,  the  weight  of  the  silica  was  obtained. 

Just  how  to  apply  this  correction  was  somewhat  of  a 
puzzle.  If  the  silica  came  from  the  quartz  vessel,  its  loss 
was  evidently  balanced  by  other  materials  absorbed ;  for  the 
weight  of  the  vessel  did  not  decrease,  and  yet  in  one  case 
the  corrosion  of  its  walls  was  observed  after  rinsing.  It 
was  finally  decided  to  assume  that  the  silica  came  from  the 
vessel,  and  subtract  its  weight  from  the  "loss  on  rinsing." 
If  part  of  it  came  from  the  sodium  vanadate,  our  method 
of  correction  would  not  be  far  wrong,  since  the  silica  would 
affect  the  observed  weight  of  sodium  chloride  over  twice  as 
much  as  that  of  the  vanadate. 

In  practically  all  cases  the  filtrate  from  the  silica  was 
tested  for  vanadium  by  the  aniline  test,  and  any  trace  thus 
indicated  was  subtracted  from  the  loss  on  rinsing. 


26 


The  results  of  five  experiments  with  quartz  appa- 
ratus are  given  in  the  Table  in  the  order  in  which  they  were 
obtained. 


Date  

1909 

A 
Colorless 

4-8550 

O.OOI4 
4-8564 
re      0.8690 

3.1876 

1910 

B 

Nearly 
colorless 

5.6388 

0.0016 
5.6404 
2.1286 
2.1282 

0.5746 

2.7028 
0.0006 

None. 
2.7022 

O.OOII 

2.7033 
121.976 
50.976 

1910 
B 

Nearly 
colorless 

4.4251 

0.0012 
4-4263 
2.1282 
2.1283 

—0.0062 

2.  122  1 
0.00094 

0.00006 
2.I2II 

O.OOO9 
2.1220 
121.946 
50.946 

1910 
E 
Nearly 
colorless 

57789 

0.0016 
57805 
2.1283 
2.1257 

0.6450 

2.7707 
0.0008 

0.00005 
2.7699 

O.OOII 

2.7710 
121.952 
50.952 

1910 
F 

Colorless 
9.4875 

O.O027 
94902 
2.1283 
2.1282 

2.4187 

4.5469 
O.OO09 

O.OOOO5 
4.5460 

O.OOlS 
4.5478 
121.097 
50.097 

Sample  

Color  of  fused 
vanadate 

Wt.     of     NaVOs 
in  air 

Correction       for 
buoyancy       of 
air    

Wt.     of     NaVO, 
in  vacuum  .  .  . 
Excess    wt.  " 
of  counter-    befo 
poise   over 
flask         .       aftei 

Excess     wt.     of 
flask  and  Na  Cl 
over     counter- 
poise 

Loss  of  Wt.   on 
rinsing 

Wt.  of  silica  .  .  . 

Wt.      of      vana- 
dium left  
Wt.      of      NaCl 
in  air    
Correction       for 
buoyancy       of 
air     .... 

None. 
2.3267 

O.OOIO 

2.3277 
121.966 
50.066 

Wt.      of      NaCl 
in  vacuum   .  .  . 
Mol.       Wt.       of 
Na  VO-, 

Atomic    Wt.    of 
vanadium     .  .  . 

27 

The  average  is  50.967  ±  0.006.  The  atomic  weights 
of  sodium  and  chlorine  were  assumed  to  be  23.00  and  35.46, 
respectively. 

The  sample  used  in  V  had  been  the  most  carefully  pre- 
pared of  any  in  the  series,  and  the  amount  of  material  used 
was  so  large  that  the  percentage  error  in  the  weighing  of  the 
sodium  chloride  would  be  considerably  diminished.  So, 
perhaps,  this  should  be  given  more  weight  in  making  up 
the  average. 

The  experiments  had  to  be  interrupted  at  this  point, 
but  it  is  intended  to  make  another  series  at  some  future 
time,  using  from  seven  to  ten  grams  of  vanadate  to  each 
experiment. 


CONCLUSION. 

This  series  of  fairly  concordant  results,  obtained  with 
material  prepared  in  several  different  ways,  proves  that 
sodium  meta-vanadate  is  a  definite  and  stable  compound 
and  that  it  can  be  prepared  free  from  excess  of  alkali  and 
from  acid  vanadates. 

The  errors  which  would  make  our  calculated  value  for 
the  atomic  weight  too  high  are :  Presence  of  acid  vanadate, 
silica  or  moisture  in  the  fused  sodium  vanadate,  and  loss 
of  sodium  chloride  by  decrepitation  or  volatilization. 

The  errors  which  would  make  the  calculated  value  too 
low  are :  Presence  of  excess  of  alkali  in  the  fused  vanadate, 
and  presence  of  moisture  in  the  sodium  chloride. 

It  is  hard  to  see  how  our  calculated  value  can  be  too 
low,  since  correction  has  been  applied  for  silica,  and  for  any 
vanadium  left  in  the  sodium  chloride,  and  the  moisture  must 
have  been  completely  removed. 

This  work  in  connection  with  that  of  Prandtl  and 
Bleyer  therefore  indicates  that  the  value  for  the  atomic 
weight  of  vanadium  is  about  51.0  instead  of  51.2. 


r.M\  KRSITY  OF  CALIFORNIA  LIBRARY, 
BERKELEY 


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20m-l,'2'J 


